RO/DI water bad for tank?

[hockey nut]

I have been using a new Ro/Di system for about a month now and noticed recently that most of my fish in three different tanks are showing signs of stress or are sick. My question is, do you need to add elements back to the Ro water? I wouldn't be to concerned if it was one tank but all three tanks are affected and after I did water changes on all three. Anyone else experience this with RO water?

[robbyville]

That is really strange! Have you tried testing your RO water to ensure that your filter is working properly?

Traditionally the idea of the RO or RO/DI is to remove everything and then put the right stuff back in through your salt mix. You may also want to check the quality of the water after mixing but prio to addition to the tank, perhaps there is a salt problem.

What are the symptoms specifically that your fish are exhibiting?

Best,

Rob

[robbyville]

I should also mention in case it has not come up, that with some ro machines the first few batches of water should be discarded until the machine "breaks in", I had not heard that until about a year ago and am not really sure if it's true, but just a thought.

[Bryan]

Correct, as the mfg usually adds a preservative or anti-fungal agent to the RO membrane.

[hockey nut]

Well, I'm still not sure what exactly caused the problems but my nitrates in two tanks are high and thats after 2 water changes. either something died in both tanks and I missed it or something got into the water. I'm testing the RO water as we speak . I have a not so funny feeling that something got into the water.
Regarding the Ro. I let it run for a couple of hours before I used any water on day 1. I mix my salt and water over a 24hr period and match temp and salinity as best as possable before I do a water change.
It also has now occurred to me that when I was away for a week I had my neighbor feed my fish and as much as I was thankfull for her doing that there may have been a small chance she had creams etc on her hands. HHHMMMM. I'll get to bottom of this yet. I'm sure the Ro is fine but I'm still going to test.
Thanks for all your help. :smile:

[hockey nut]

Has anyone ever tested the ph on their RO water. Mine is below 5.0 Thats very acidic. When I add my salt it only brings it back up to 7.5 to 7.8 . Not enough for marine standards. Could someone pls check their Ph on their RO water and let me know. The water out of the tap is a drinkable PH of 7.

Thank you.

[Canadian Man]

I believe the ph of ro/di water is not possible to mesure....well I suppose if your using a ph meter it will give you some sort of reading.

If you think about it there is nothing in the water after the ro/di unit so the ph reading will be inaccurate.

This might not be true but i'm just thinking of what ph actually is and how it's mesured. :biggrin:

[IslandReefer]

I will second that:
pH meters need at least a trace of electolyte to give a reading even close to accurate. Add just a smidge of table salt to your RO water and see what happens.

[StirCrazy]

Well, I'm still not sure what exactly caused the problems

It also has now occurred to me that when I was away for a week I had my neighbor feed my fish

sound slike she was feeding to much to me.

Steve